       :line <integer>
       :column <integer>}*]
 
-   :file must be a URL path (without protocol) relative to :output-dir."
+   :file must be a URL path (without protocol) relative to :output-dir. The
+   returned mapped stacktrace will also contain :url entries to the original
+   sources if it can be determined from the classpath."
   ([stacktrace] (mapped-stacktrace stacktrace nil))
   ([stacktrace opts]
     (let [read-source-map' (memoize read-source-map)

                          (if ns-info
                            source-file
                            (io/file rfile)))
                        (str (System/getProperty "user.dir") File/separator) "")]
            {:function name'
             :file     file'
             :line     line'
             :column   column'}))))))

(defn print-mapped-stacktrace
  "Given a vector representing the canonicalized JavaScript stacktrace

     :output-to "samples/hello/out/hello.js"
     :source-map true})

  (mapped-stacktrace
    [{:file "hello/core.js"
      :function "first"
